This invention relates to a plasma processing unit, a window member for a plasma processing unit and an electrode plate for a plasma processing unit.
In Japanese Patent Laid-Open Publications No. 4-94533 and No. 10-64884, a technique has been proposed wherein a window which a beam of light can penetrate is provided at a central portion of an electrode facing another electrode on which a wafer is placed, and wherein reflection of a beam of light given from an outside of an etching unit to the wafer is detected by means of a detector disposed at the outside of the etching unit in order to monitor an etching state. In addition, in Japanese Patent Laid-Open Publication No. 2-201924, a technique has been proposed wherein two optical fibers extend through an ozone-dispersion plate from an outside of a heating-type ashing unit, and wherein a beam of light is given to a wafer facing the ozone-dispersion plate through one of the optical fibers and reflection of the beam from the wafer Is received through the other of the optical fibers by means of a detector disposed at the outside of the unit in order to monitor an ashing state.
In cases of the monitoring techniques disclosed in the Japanese Patent Laid-Open Publications No. 4-94533 and No. 10-64884, an electric field between electrodes may be affected by a shape of the window for monitoring and a shape of each of the electrodes, and hence it may be difficult to uniformly conduct a plasma process. However, the shapes thereof are not taken into consideration at all. In addition, if an optical fiber reaches a surface of an electrode as shown in the latter publication, an electric field between electrodes may be affected by the optical fiber, and furthermore reaction products may stick to the optical fiber so that a transmissivity of the optical fiber may be deteriorated. However, the points are not taken into consideration at all. In cases of the monitoring technique disclosed in the Japanese Patent Laid-Open Publications No. 2-201924, since the optical fibers extend through the ozone-dispersion plate and are subjected to an ashing environment, reaction products may stick to the optical fibers so that a transmissivity of the optical fibers may be deteriorated. However, the points are not taken into consideration at all.
In some types of plasma processing units, dispersion holes for supplying a gas are formed in the whole surface of an electrode. Regarding a window for monitoring in the some types of plasma processing units, a larger window for monitoring is necessary in order to secure a quantity of light sufficient for monitoring, in comparison with the gas-dispersion holes. Thus, a plurality of the gas-dispersion holes are sacrificed for the window for monitoring, that is, the process gas cannot be supplied through the sacrificed gas-dispersion holes. Therefore, there is a problem that density of the process gas may become ununiform between the electrodes, and hence that plasma density may become ununiform, and hence that uniformity of the plasma process may be deteriorated. In addition, if the size of a window for monitoring is large, the plasma may be diffused into an optical path of the window for monitoring and hence suspended particles and/or reaction products in the plasma may fog up the quartz glass in a short time (for example about 30 minutes), so that it may become impossible to monitor the processing state of a wafer W in the short time.
This invention is intended to solve the above problems. The object of this invention is to provide a plasma processing unit, a window member for a plasma processing unit and an electrode plate for a plasma processing unit, in which a process gas can be uniformly supplied into a processing container to conduct a uniform plasma process even if a window for monitoring is provided. In addition, this invention also provides a plasma processing unit, a window member for a plasma processing unit and an electrode plate for a plasma processing unit, in which the processing state of an object to be processed can be monitored for a long time.
This invention is a plasma processing unit including: a processing container; a first electrode disposed in the processing container, the first electrode having a plurality of gas-dispersion holes for supplying a process gas into the processing container and an opening for a measurement light; a second electrode arranged on one side of and a predetermined gap away from the gas-dispersion holes and the opening of the first electrode; a power source unit that applies electric power between the first electrode and the second electrode and that generates plasma between the first electrode and the second electrode; and a window member having an optical path that adjacently communicates with the other side of the opening for the measurement light; wherein the gas-dispersion holes are formed in a predetermined arrangement, and the opening is formed separately from the gas-dispersion holes without disturbing the arrangement of the gas-dispersion holes.
Preferably, the first electrode has a space, the space being connected to a process-gas supplying tube that supplies the process gas and communicating with the gas-dispersion holes.
Preferably, the space is shut off from the opening. More preferably, the space is also shut off from the optical path.
In addition, preferably, the opening and the optical path have such a long and narrow shape that it is hard for the plasma to come into the opening and the optical path. In the case, preferably, the opening and the optical path have an aspect ratio not less than 7, particularly an aspect ratio of about 9.8.
In addition, preferably, it further includes a laser-measurement unit that emits a laser beam into the processing container through the optical path of the window member and that receives and measures reflection of the beam from the processing container through the optical path.
In addition, preferably, the window member has a transparent plate arranged with an inclination with respect to a plane perpendicular to the optical path, on the opposite side to the opening side of the optical path.
Preferably, the gas-dispersion holes are formed in a substantially uniform arrangement in a whole surface of the first electrode.
Preferably, the opening is formed in a central portion of the first electrode, and one or more additional openings are also formed in the central portion of the first electrode.
In addition, this invention is a window member for a plasma processing unit, the plasma processing unit including: a processing container; a first electrode disposed in the processing container, the first electrode having a plurality of gas-dispersion holes for supplying a process gas into the processing container and an opening for a measurement light; a second electrode arranged on one side of and a predetermined gap away from the gas-dispersion holes and the opening of the first electrode; and a power source unit that applies electric power between the first electrode and the second electrode and that generates plasma between the first electrode and the second electrode; wherein the gas-dispersion holes are formed in a predetermined arrangement, the opening is formed separately from the gas-dispersion holes without disturbing the arrangement of the gas-dispersion holes, the first electrode has a space, the space being connected to a process-gas supplying tube that supplies the process gas and communicating with the gas-dispersion holes, and the space is shut off from the opening; the window member comprising: an optical path that adjacently communicates with the other side of the opening for the measurement light; wherein the optical path is adapted to be shut off from the space.
In the case, preferably, the opening and the optical path are adapted to form such a long and narrow shape that it is hard for the plasma to come into the opening and the optical path.
More preferably, a window member for a plasma processing unit further comprises: a transparent plate arranged with an inclination with respect to a plane perpendicular to the optical path, on the opposite side to the opening side of the optical path.
In addition, this invention is an electrode plate for a plasma processing unit comprising: a plurality of gas-dispersion holes for supplying a process gas; and an opening for a measurement light; wherein the gas-dispersion holes is formed in a predetermined arrangement, and the opening is formed separately from the gas-dispersion holes without disturbing the arrangement of the gas-dispersion holes.